WASHINGTON (CNN) -- U.S. officials
question the veracity of four former Salvadoran
guardsmen who, for the first time, say that they
raped and killed 3 U.S. nuns and a lay worker in
1980 on orders from superiors.

Government sources told CNN that the
guardsmen have repeatedly offered to give more
information on the crime in return for amnesty.
One source said the offer does not necessarily
mean the guardsmen are lying, but that it does
raise questions.

The guardsmen made their admissions in interviews with Scott
Greathead and Robert Weiner of the New York-based Lawyers
Committee for Human Rights, which represents families of the
victims. George Black, research and editorial director of the
committee, confirmed the comments, which were reported in
Friday's editions of The New York Times.

"I can confirm it's an accurate report," Black said Friday, adding
that he could not provide details of the guardsmen's admissions.

The Times quoted one of the guardsmen as saying his superior told
them, "Don't be worried. This is an order that comes from higher
levels, and nothing is going to happen to us."

That superior, Luis Antonio Colindres Aleman, was also
convicted, but he is held in a separate prison and declined to talk
to the investigators.

U.N. report claimed a cover-up

El Salvador and the United States have always maintained that the
men acted on their own, but human rights groups insisted that the
murders were ordered, approved and directed by the military.

U.S. State Department spokesman James Rubin repeated that
position Friday during a briefing.

"A U.S. federal judge went down there and conducted an
exhaustive review of the killings, concluding that the guardsmen
were not -- I emphasize the word 'not' -- following orders from
senior officers," Rubin said.

"If, however, there is any new evidence that emerges, we would
want to see the Salvadorans vigorously urge the government...to
investigate and, if warranted, to prosecute those implicated."

In 1993, a U.N. report concluded that Col. Carlos Eugenio Vides
Casanova, director of the National Guard in 1980, and Minister of
Defense Gen. Jose Guillermo Garcia had organized an official
cover-up of the incident.

According to public record, both men were granted residence in
the United States and live in Florida.

Government sources said that if there is credible evidence of their
involvement in the incident, there should be a probe of how they
received their visas. As of now, the officials say, there is no reason
to question their residency.

'An order from above'

The slayings of the nuns -- Maryknoll nuns Ita Ford, 40, Maura
Clarke, 49, and Dorothy Kazel, 41, and lay worker Jean
Donovan, 27 -- came during a bloody civil war launched the
preceding year by leftist guerrillas against a repressive military
government.

The United States was engaged in the early stages of a
decade-long, $7 billion effort to prevent the guerrillas from coming
to power. The war finally ended in 1992 after claiming the lives of
nearly 70,000 people.

The former guardsmen were convicted of murder in 1984,
sentenced to 30 years in prison and have twice been declared
ineligible for amnesty offered at the end of the war because their
crime was classified as non-political.

One guardsman told the Times, "What I remember is that we were
told that we had to carry out a special service" by Sgt. Colindres
Aleman. He added that "when we consulted with him as to why, he
said it was an order from above."

'The system just didn't work that way'

The Times said the four former guardsmen stressed that they did
not know who in the chain of command issued the original order to
kill the women.

William Ford, brother of Ita Ford and an attorney, said the
statements confirmed what the victims' families had always
believed.

"I've had dozens of conversations in El Salvador over the years
with people who said it would be simply unthinkable for any group
of low-ranking guardsmen to kill four North American women
without having been ordered to do so, that the system just didn't
work that way," Ford told the Times.